Thermostatically controlled heat shield for window units in pyrolytic ovens

ABSTRACT

A window unit for use in the oven door of a self-cleaning oven comprising a pair of spaced glass panels separated by a spacer and clamped together by a peripheral clamping flange with a series of pivoted louvers disposed between the glass panels and supported at their opposite ends by the spacer, and a thermally responsive actuator for automatically pivoting the louvers to a closed position to prevent radiation of excessive heat to the outer glass panel when the oven is on the cleaning cycle. The louvers are automatically opened by the actuator to permit viewing through the window unit during normal cooking operations.

United States Patent Larkin 1 Feb. 22, 1972 [54] THERMOSTATICALLY CONTROLLED 3,565,054 2/1971 Smith et al. ..126/200 X HEAT SHIELD FOR WINDOW UNITS IN PYROLYTIC OVENS Primary Examiner-Carroll B. Dority, Jr.

Att0rneyWhittemore, Hulbert & Belknap [72] Inventor: Robert B. Larkin, Farmington, Mich. [73] Assignee: Mills Products, Inc., Farmington, Mich. [57] ABSTRACT [22] Filed, Oct. 26 1970 A window unit for use in the oven door of a self-cleaning oven comprising a pair of spaced glass panels separated by a spacer [21] Appl. No.: 83,793 and clamped together by a peripheral clamping flange with a series of pivoted louvers disposed between the glass panels and supported at their opposite ends by the spacer, and a theri gi: mally responsive actuator for automatically pivoting the lou- 58] Field I200 198 vers to a closed position to prevent radiation of excessive heat to the outer glass panel when the oven is on the cleaning cycle. The louvers are automatically opened by the actuator to per- [56] References cued mit viewing through the window unit during non'nal cooking UNITED STATES PATENTS operations- 3,433,213 3/1969 Huff et al. ..l26/200 X 9 Claims, 5 Drawing Figures PMENlEnrzezz I972 I 3, 643 647 SHEET 2 0F 2 INVENTOR.

THERMOSTATICALLY CONTROLLED HEAT SHIELD FOR WINDOW UNITS IN PYROLYTIC OVENS In self-cleaning ovens the interior of the oven reaches temperatures of 950 F. or more in order to clean the oven by the pyrolytic process. In ovens equipped with a window in the oven door it is necessary to provide some means for preventing excessive temperatures on the outer glass panel of the window unit. A common method of reducing the temperature of the outer glass consists of providing a manually movable shield which is connected to the oven door latch and controls in such a way that the cleaning cycle cannot be initiated unless the shield is in the closed position blocking radiation of heat to the outer glass. Such structures require considerable space within the oven door and various linkages and locking mechanisms to raise and lower the shield and to hold it in the closed position during the cleaning cycle.

Other efforts to reduce radiation of heat to the outer glass consist in coating one or more of the glass panels with a reflective coating to reflect the radiant heat back into the oven. However, the reflective coating greatly reduces visibility through the window unit and is objectionable for that reason.

The present invention provides a self-contained window unit for use in an oven door in a self-cleaning oven in which a series of pivoted louvers are thermostatically controlled so as to rotate from an open to a closed position when the oven reaches a predetermined temperature. The provision of thermostatically actuated louvers which are opened and closed in accordance with oven temperatures eliminates the expensive tracks and linkages that are necessarily associated with conventional arrangements in which a shield is manually elevated over the window opening and mechanically interlocked with the door latching mechanism to insure that the shield will be in place when the cleaning cycle is initiated. The thermostatically controlled louvers have the further advantage of not requiring a reflective coating on any of the glass panels, thereby maintaining clear visibility through the window'unit. The inner glass panel is exposed to the oven and therefore reaches a higher and more uniform temperature, resulting in better cleaning than is possible when the inner glass is provided with a reflective coating. The louver construction of this invention is also readily adaptable to different size window units.

In the drawings:

FIG. 1 is a perspective view, with parts broken away, of a window unit according to the present invention;

FIG. 2 is a vertical sectional view through an oven and an oven door having the window unit installed therein;

FIG. 3 is an enlarged fragmentary perspective view of a portion of the window unit;

FIG. 4 is a horizontal sectional view taken on line 44 of FIG. 2; and

FIG. 5 is a sectional view similar to FIG. 4 but showing the louvers in their closed position.

In FIG. 2 there is disclosed a portion of an oven having an access opening 12 adapted to be closed by an oven door 14 provided with a handle 16 and a suitable hinge mechanism (not shown) by which the door is hinged along the lower edge of the opening 12 in the oven. The window unit of this invention is indicated generally at 18 and comprises an inner glass panel 20, an outer glass panel 22, a spacer 24 interposed between the glass panels and 22, a clamping frame 26 for clamping the panels 20 and 22 against the spacer 24, and a series of pivoted louvers 28 disposed between the glass panels 20 and 22 and pivotally mounted at their opposite ends on the top and bottom sides of the spacer 24.

The spacer 24 may comprise two channel-shaped sheet metal members each having a longer leg 30 forming the top or bottom edge of the spacer and a shorter leg 32 forming one of the vertical legs of the spacer. The legs 30 and 32 have outwardly turned flanges 34 which are adapted to seat against the peripheral edges of the glass panels 20 and 22. The legs 30 of the two members forming the spacer 24 are provided with tabs 36 which may be welded or otherwise secured to the adjacent end of the shorter leg 32 ofeach member to provide a continuous channel-shaped spacer between the glass panels.

The legs 30 of the spacer are provided with a series of equally spaced holes for pivotally supporting the louvers 28. Each of the louvers has a pivot member 38 press fitted onto its opposite ends with the pivot members being provided with pins 40 which extend through the holes in the spacer. Cams 42 are fitted over the projecting ends of the pins 40 on the pivot members 38 which are secured to the upper ends of the louvers 28. The pins may then be staked over to rigidly secure the cam members 42 to the louvers 28 so that the louvers will be rotated with the cam members 42. Each of the cam members has a flat body portion 44 engaging against the spacer and diametrically opposed cars 46 and 48.

An actuating member 50 having an inverted channelshaped cross section is provided in one wall 52 thereof with notches 54 which are fitted over the cutout portions 56 provided on the cars 48 of cam members 42 as shown in FIG. 3. The other sidewall 58 of the actuator member 50 is fitted inside of the cars 46 on the cam members 42 and the cars 46 and 48 thus serve to confine the sidewalls 52 and 58 of the actuator member 58 therebetween.

At one end thereof the actuator member 50 is provided with a downwardly bent end 60 which may be spot welded or otherwise secured to the free end 62 of a thermostatic actuator in the form of a bimetal strip 64 which is secured at its lower end to the spacer 24, such as by the screws 66 as shown in FIG. I. The other end of the actuator member 50 is freely movable relative to spacer 24 and the actuator member 50 is supported on the cam members 42 and located between the cars 46 and 48 thereof, as previously described.

The clamping frame 26 is of channel-shaped cross section and may comprise two L-shaped pieces secured together at opposing corners in any suitable manner. The clamping frame 26 engages the outer surfaces of the glass panels 20 and 22 at their peripheral edges and the inner leg 70 of the clamping frame may carry a suitable seal 72, such as an asbestos cord or the like, or a separate molding strip may be clamped against the inner glass panel 20 by the clamping frame for the purpose of supporting the sealing member 72 for engagement with the flange 74 on the inner door panel 76 which defines the window opening in the oven door 14. Two or more mounting brackets '78 may be secured to the clamping frame 26 by means of which the window unit may be secured to the oven door within the window opening.

It will be seen that the actuator member 50 is movable longitudinally thereof as the bimetal strip 64 is deflected between the two positions thereof shown in FIG. 3. When the oven temperature is at or below the maximum cooking temperature of about 500 to 550 F. the bimetal actuator 64 will remain in the position shown in solid lines in FIG. 3, which corresponds to the position of the louvers shown in FIG. 4 from which it will be seen that the louvers lie in planes perpendicular to the glass panels 20 and 22 so as to provide for viewing the interior of the oven. When the oven controls are set to initiate a cleaning cycle the bimetal actuator 64 will begin to flex shortly after the oven temperature exceeds the normal cooking range, thereby pulling the actuator member 50 toward the right as viewed in FIGS. 1 and 3. The movement of the actuator member 50 will cause the left-hand edges of the notches 54 therein to engage the cars 48 to rotate the cam members 42 in a counterclockwise direction, thereby rotating the louvers 28 to the closed position shown in FIG. 5. The bimetal actuator 64, being located within the window unit, will not immediately assume the same temperature that prevails within the oven when the cleaning cycle is initiated, but the lag in temperature of the bimetal will not be great and the bimetal is chosen so that it will completely close the louvers before the maximum cleaning temperature is reached and before the outer glass panel has had sufficient time to become excessively hot. The bimetal is chosen to have no movement in a louver closing direction at temperatures within the normal cooking range, and then to warp relatively rapidly at oven temperatures in excess of the cooking range.

The cars 46 and 48 on the cam member 42 prevent any sidewise motion of the actuator member 50 which might disengage it from the cam members. The clamping frame 26 overlies actuator 50 and is closely spaced thereto to prevent outward displacement of the actuator to prevent its disengagement from the cam members 42, thereby insuring positive actuation of the member 50 by the bimetal strip 64 in response to oven temperatures. The width of the louvers 28 and the spacing thereof are such that there is preferably a slight overlap of the ends of adjacent louvers in the closed position thereof, as shown in FIG. 5. If desired, the inner surfaces of the louvers 28 may be provided with a reflective coating to reduce the transmission of heat to the outer glass panel 22.

It is contemplated that the window unit described herein may be used in conventional door constructions which are employed in self-cleaning ovens, and a typical installation is illustrated in FIG. 2 wherein it will be noted that the oven door includes a third glass panel 80 which is substantially coextensive in length and width with the door 14. The space 82 between the glass panel 80 and the outer glass 22 of the window unit constitutes an air passage having its inlet 84 at the bottom thereof and its outlet 86 in the top wall of the door 14. A natural circulation of air will take place upwardly through the passage 82 to aid in reducing the temperature of the glass 80.

While a bimetallic type of thermostatic element has been described for effecting movement of the actuator member 50, it will be obvious that other thermally responsive devices may be used to control movement of the actuator member.

The self-contained unit described herein has many advantages over conventional constructions used in self-cleaning ovens which employ a manually movable shield interlocked with the door latch. Such conventional constructions impose limitations on the height of the window since a storage space for the shield must be provided within the door below the window, while with the present invention no such limitations are present and the space below the unit can contain insulation. The present unit also eliminates the linkages and supporting structure for the shield used in conventional heat shields, thereby resulting in a considerable reduction in the weight of the unit. The present unit is also much more easily adaptable to the manufacture of units of different sizes since onlythe length of the louvers or the length of the spacer and the actuator member need be changed.

What I claim as my invention is:

1. A window unit for use in the oven door of a self-cleaning oven, comprising a pair of glass panels, a spacer between said glass panels at the peripheral edges thereof, a series of louvers disposed between said panels and having their opposite ends pivotally mounted on opposing sides of said spacer, a longitudinally movable actuator operable to rotate said louvers between open and closed positions, and thermally responsive means operable to shift said actuator in accordance with oven temperatures.

2. A window unit according to claim 1, including a cam member secured to each of said louvers, said actuator being supported by and engaging said cam members.

3. A window unit according to claim 2 wherein said louvers have a pin at one end projecting through said spacer, said cam members being secured to said projecting ends of said pins.

4. A window unit according to claim 3, wherein said cam members have means thereon preventing displacement of said actuator in a direction normal to the axis of said pins.

5. A window unit according to claim 3, including a clamping frame surrounding the edges of said glass panels for clamping the same against said spacer, said clamping frame enclosing said actuator and said thermally responsive means.

6. A window unit according to claim 5 wherein said clamping frame prevents displacement of said actuator in a direction parallel to the axis of said pins.

7. A window unit according to claim 1 wherein said thermally responsive means comprises a bimetal member having one end secured to said spacer and its other end secured to one end of said actuator.

8. A window unit for use in the oven door of a self-cleaning oven including a pair of glass panels and a spacer therebetween, a series of rotatable louvers between said panels, thermally responsive means mounted on said unit, and actuator means interconnecting said louvers and said thermally responsive means for rotating said louvers between open and closed positions in response to oven temperatures.

9. A window unit according to claim 8, including a clamping frame surrounding the edges of said glass panels for clamping the same against saidspacer, said thermally responsive means and actuator means being disposed within said clamping frame. 

1. A window unit for use in the oven door of a self-cleaning oven, comprising a pair of glass panels, a spacer between said glass panels at the peripheral edges thereof, a series of louvers disposed between said panels and having their opposite ends pivotally mounted on opposing sides of said spacer, a longitudinally movable actuator operable to rotate said louvers between open and closed positions, and thermally responsive means operable to shift said actuator in accordance with oven temperatures.
 2. A window unit according to claim 1, including a cam member secured to each of said louvers, said actuator being supported by and engaging said cam members.
 3. A window unit according to claim 2 wherein said louvers have a pin at one end projecting through said spacer, said cam members being secured to said projecting ends of said pins.
 4. A window unit according to claim 3, wherein said cam members have means thereon preventing displacement of said actuator in a direction normal to the axis of said pins.
 5. A window unit according to claim 3, including a clamping frame surrounding the edges of said glass panels for clamping the same against said spacer, said clamping frame enclosing said actuator and said thermally responsive means.
 6. A window unit according to claim 5 wherein said clamping frame prevents displacement of said actuator in a direction parallel to the axis of said pins.
 7. A window unit according to claim 1 wherein said thermally responsive means comprises a bimetal member having one end secured to said spacer and its other end secured to one end of said actuator.
 8. A window unit for use in the oven door of a self-cleaning oven including a pair of glass panels and a spacer therebetween, a series of rotatable louvers between said panels, thermally responsive means mounted on said unit, and actuator means interconnecting said louvers and said thermally responsive means for rotating said louvers between open and closed positions in response to oven temperatures.
 9. A window unit according to claim 8, including a clamping frame surrounding the edges of said glass panels for clamping the same against said spacer, said thermally responsive means and actuator means being disposed within said clamping frame. 